Efficacy and safety of nivolumab for patients with pre-treated type B3 thymoma and thymic carcinoma: results from the EORTC-ETOP NIVOTHYM phase II trial.

BACKGROUND: Thymic malignancies are rare intrathoracic tumors, which may be aggressive and difficult to treat. They represent a therapeutic challenge in the advanced/metastatic setting, with limited treatment options after the failure of first-line platinum-based chemotherapy. They are frequently associated with autoimmune disorders that also impact oncological management. MATERIALS AND METHODS: NIVOTHYM is an international, multicenter, phase II, two-cohort, single-arm trial evaluating the activity and safety of nivolumab [240 mg intravenously (i.v.) q2 weeks] alone or with ipilimumab (1 mg /kg i.v. q6 weeks) in patients with advanced/relapsed type B3 thymoma or thymic carcinoma, after exposure to platinum-based chemotherapy. The primary endpoint is progression-free survival rate at 6 months (PFSR-6) based on RECIST 1.1 as per independent radiological review. RESULTS: From April 2018 to February 2020, 55 patients were enrolled in 15 centers from 5 countries. Ten patients (18%) had type B3 thymoma and 43 (78%) had thymic carcinoma. The majority were male (64%), and the median age was 58 years. Among the 49 eligible patients who started treatment, PFSR-6 by central review was 35% [95% confidence interval (CI) 22% to 50%]. The overall response rate and disease control rate were 12% (95% CI 5% to 25%) and 63% (95% CI 48% to 77%), respectively. Using the Kaplan-Meier method, median progression-free survival and overall survival by local assessment were 6.0 (95% CI 3.1-10.4) months and 21.3 (95% CI 11.6-not estimable) months, respectively. In the safety population of 54 patients, adverse events (AEs) of grade 1/2 were observed in 22 (41%) patients and grade 3/4 in 31 (57%) patients. Treatment-related AEs of grade 4 included one case of neutropenia, one case of immune-mediated transaminitis, and two cases of myocarditis. CONCLUSIONS: Nivolumab monotherapy demonstrated an acceptable safety profile and objective activity, although it has been insufficient to meet its primary objective. The second cohort of NIVOTHYM is currently ongoing to assess the combination of nivolumab plus ipilimumab.

Pathophysiology and human cancer risk assessment of pharmaceutical-induced thymoma in carcinogenicity studies.

Thymoma, a tumor of thymic lymphocytes or thymic epithelial cells (TECs), is a common spontaneous tumor in Wistar Han rats, especially in females with up to 18% incidence in controls. In addition to sex, there are rat strain differences in background incidence of thymomas such as Sprague Dawley versus Wistar Han rats. Human thymomas are very rare and without clear differences in incidence between males and females. Immunomodulatory and anti-inflammatory pharmaceutical drug classes, including Janus kinase inhibitors, increase the incidence of benign thymoma in two-year rat carcinogenicity studies. Potential non-genotoxic mechanisms that might contribute to the pathogenesis of thymoma development in one sex (female) Wistar Han rats include: (1) hormonal differences, (2) high proliferation rate of TECs, (3) delayed physiologic thymic involution, and/or (4) significant level of immunosuppression at high doses of a pharmaceutical drug. Factors to consider in the human cancer risk assessment of pharmaceutical-induced thymoma are: the genotoxicity of the test article, sex and strain of rats, exposure safety margins, and pathophysiologic differences and similarities of thymoma between rats and humans. Totality of weight of evidence approach and available data suggest thymomas observed in carcinogenicity studies of pharmaceutical drugs are not relevant for human risk at clinically relevant therapeutic doses.

Sustained antitumor response to lenvatinib with weekend-off and alternate-day administration in chemotherapy-refractory thymic carcinoma: a case report.

Lenvatinib is a multitargeted kinase inhibitor and maintaining its dose intensity has been shown to be beneficial in patients with thyroid and hepatocellular carcinomas. However, most patients require lenvatinib interruption and dose reduction due to the high incidence of adverse events (AEs). Lenvatinib was recently approved in Japan for patients with unresectable thymic carcinoma; however, real-world evidence of its clinical benefit is limited. Here, we report the case of chemotherapy-refractory thymic carcinoma in a patient who was administered a starting dose of lenvatinib using a 5-day on/2-day off (weekend-off) protocol, followed by alternate-day administration after fatigue onset derived from overt or subclinical hypothyroidism. Consequently, the patient exhibited a durable response to lenvatinib, with a 17-month progression-free survival without any severe or intolerable AEs. The present case suggests that maintaining lenvatinib dose intensity using such alternative administration regimens contributes to favorable clinical outcomes in thymic carcinoma.

Microsatellite instability detected in tumor-related genes in C57BL/6J mice with thymic lymphoma induced by N-methyl-N-nitrosourea.

Microsatellite instability (MSI) has been observed within tumors and found to be closely associated with the degree of malignancy and prognosis in tumors. However, whether MSI in tumor-related genes can be induced by a chemical and whether a connection exists between MSI and tumors remain unclear. In the present study, we detected MSI in the tissues of N-methyl-N-nitrosourea (MNU) treated mice by targeting to 5, 29, 30 microsatellite loci in 3 mismatch repair (MMR) genes, 1 DNA repair gene, and 5 tumor suppressor (TS) genes, respectively. Among 26 mice survived in the MNU-group, 18 (69%) mice presented thymic lymphomas. Moreover, 61% (11/18) of the tumors metastasized to the other organs, including the liver, spleen, and kidney. We examined 104 tissues from MNU-treated mice using the 64 loci, and found 8 MSI events involved 4 loci in 4 tissues types. The MSI incidence in MMR, DNA repair, and TS genes was 67% (2/3), 0% (0/1) and 40% (2/5), respectively. MSI occurrence in tumor and non-tumor tissues was 5.6% (1/18) and 0% (0/8) and that in metastasis and non-metastasis tissues was 7.1% (1/14) and 9.4% (6/64), showing no significant difference. MSI loci in intronic regions of Atm, Msh6 and p21 and MSI in the 3'UTR of Pms2 were detected in MNU-treated mice. Specifically, we found a loss of heterozygosity in intron of Atm (ATM-8) in one metastasis mouse. Four similar events occurred in p21 gene intron (P21-1) of another non-metastasis mouse. Another MSI was a heterozygous mutation existed in an Msh6 allele (MSH6-2) in metastasis mouse. We also found a homozygous 2-bp insertion in the 3'UTR of Pms2 in two non-metastasis mice. These results imply that MNU can induce MSI in MMR and TS genes in C57BL/6J mice. MSI frequency does not seem to be associated with tumorigenesis or metastasis.

Developmental exposure to 2,3,7,8 tetrachlorodibenzo-p-dioxin attenuates later-life Notch1-mediated T cell development and leukemogenesis.

Over half of T cell acute lymphoblastic leukemia (T-ALL) patients have activating mutations in the Notch gene. Moreover, the contaminant 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD) is a known carcinogen that mediates its toxicity through the aryl hydrocarbon receptor (AHR), and crosstalk between activated AHR and Notch signaling pathways has previously been observed. Given the importance of Notch signaling in thymocyte development and T-ALL disease progression, we hypothesized that the activated AHR potentiates disease initiation and progression in an in vivo model of Notch1-induced thymoma. This hypothesis was tested utilizing adult and developmental exposure paradigms to TCDD in mice expressing a constitutively active Notch1 transgene (Notch(ICN-TG)). Following exposure of adult Notch(ICN-TG) mice to a single high dose of TCDD, we observed a significant increase in the efficiency of CD8 thymocyte generation. We next exposed pregnant mice to 3µg/kg of TCDD throughout gestation and lactation to elucidate effects of developmental AHR activation on later-life T cell development and T-ALL-like thymoma susceptibility induced by Notch1. We found that the vehicle-exposed Notch(ICN-TG) offspring have a peripheral T cell pool heavily biased toward the CD4 lineage, while TCDD-exposed Notch(ICN-TG) offspring were biased toward the CD8 lineage. Furthermore, while the vehicle-exposed NotchICN-TG mice showed increased splenomegaly and B to T cell ratios indicative of disease, mice developmentally exposed to TCDD were largely protected from disease. These studies support a model where developmental AHR activation attenuates later-life Notch1-dependent impacts on thymocyte development and disease progression.

The susceptibility of inbred mice to the production of malignant thymoma by N-methyl-N-nitrosourea.

The susceptibility of inbred mice to the induction of malignant thymoma by N-methyl-N-nitrosourea (MNU) has been quantified and compared. Strain differences emerged and this was also apparent in congenic lines of C57BL/10 mice, differing at the H-2 locus. However, different strains of inbred mice, with identical H-2 haplotypes, also showed varying susceptibility to MNU, indicating that the role of the MHC was not a simple one, but apparently depended on other, undefined genes. Proficiency of repair of O6-methylguanine by thymic tissue was not responsible for these strain differences and the increased resistance to induction of thymoma by MNU in older mice was due to age-dependent changes within the thymus gland. Interestingly, the thymus of older mice, grafted with neonatal thymic tissue, still provided a suitable environment for the development of thymic tumours.

Malignant thymoma in a patient with growth hormone deficiency during growth hormone therapy.

Malignant thymoma was found in an 8-year-old Japanese boy with growth hormone (GH) deficiency who had received GH therapy for 3 years and 5 months. There may be a possible relationship between the occurrence of malignant thymoma and GH therapy.

Chemical induction of thymomas in AKR mice: interaction of chemical carcinogens and endogenous murine leukemia viruses. Comparison of N-methyl-N-nitrosourea and methyl methanesulphonate.

The time course of development of thymic lymphoma, which occurs spontaneously in mice of the AKR strain, is accelerated by the methylating agents N-methyl-N-nitrosourea (MNU) and methyl methanesulphonate (MMS). Since MNU is a potent mutagen inducing G----A transition mutations and MMS a relatively weak mutagen, it was of interest to examine the genetic alterations associated with each class of the chemically induced tumors and to compare these alterations with those found in the spontaneous tumors. The same spectrum of genetic alterations was found for MMS-induced and spontaneous thymomas. Both showed rearrangements of c-myc and Pim-1 genes that appeared to result from integration of recombinant mink cytopathic focus-forming (MCF) proviruses but failed to reveal evidence for activation of ras oncogenes, either by DNA transfection experiments or by hybridization of DNA to specific oligonucleotide probes. Some alteration in c-myc and Pim-1 genes were also found in MNU-induced tumors, but, mainly, these involved integration of ecotropic-like rather than recombinant MCF viruses. Furthermore, MNU-induced tumors frequently (in 24% of thymomas) contained G----A transition mutations, activating the Ki-ras oncogene at codon 12 position 2. Another feature that distinguishes the MNU-induced tumors from those occurring in untreated and MMS-treated mice was the consistently high level of c-myc mRNA that occurred in the absence of c-myc gene rearrangement. Taken together, the data indicate that the mechanisms of development of tumors following treatment with MNU and MMS are distinct, and that the effect of MMS is probably to speed up the process of viral leukemogenesis.

Induction of thymic lymphomas and squamous cell carcinomas following topic application of isopropyl methanesulfonate to female Hsd:(ICR)BR mice.

The goal of these experiments in female Hsd:(ICR)Br mice was to determine whether the direct-acting SN1 alkylating carcinogen isopropyl methanesulfonate (IMS) is carcinogenic and to compare its effects with those of the direct-acting SN2 methyl homologue, methyl methanesulfonate (MMS). The compounds were administered by topical application and s.c. injection. Analysis at the 288th day of mice receiving s.c. injections of IMS and MMS was the subject of a previous report (A. Segal et al., Proc. Soc. Exp. Biol. Med., 183: 132-135, 1986). The s.c. and topical application experiments were terminated at the 450th day and the final results are reported in this paper. In mice treated by s.c. injection with IMS, thymic lymphomas were observed in at least 20 of 32 mice, the first at the 40th day, and neoplasms were not observed at the injection site. Of the 30 MMS-treated mice, 11 developed sarcomas at the injection site and one thymic lymphoma was observed. In mice treated topically with IMS, thymic lymphomas were observed in 20 of 30 treated mice, the first at the 102nd day, and squamous cell carcinomas at the injection site were observed in 9 mice. Neither squamous cell carcinomas nor thymic lymphomas were observed in 30 mice following topical application of MMS. The direct-acting SN2 aklylating carcinogen beta-propiolactone was also administered by topical application. At the 450th day, at the same dose used for MMS (40 mumol/application), papillomas of the skin were observed in 25 of 30 treated mice, squamous cell carcinomas of the skin were seen in 17 mice, and one thymic lymphoma was observed. The results suggest that the rapid induction of thymomas by IMS may be related to its ability to alkylate exocyclic oxygen atoms in DNA of hemopoietic cells and also to a sensitivity of these cells to such lesions.

Induction of thymomas by N-methyl-N-nitrosourea in AKR mice: interaction between the chemical carcinogen and endogenous murine leukaemia viruses.

AKR mice develop thymomas spontaneously when greater than 6 months old but when young AKR mice are treated with N-methyl-N-nitrosourea (MNU) they develop thymomas at 3-6 months of age. In this study the potential role of oncogene activation in the development of both the spontaneous and MNU-induced thymomas in AKR mice has been examined by DNA transfection into NIH3T3 mouse fibroblasts and by Southern analysis of tumour DNA. The results show that a high proportion of MNU-induced thymomas contain activated cellular rasK while no activated cellular ras genes were detected in spontaneous thymomas. Southern analysis of tumour DNA revealed that 2/30 spontaneous tumours and 2/52 MNU-induced tumours contained alterations in the c-myc gene while 5/29 spontaneous tumours and 6/56 MNU-induced tumours contained alterations in the Pim-1 gene. A more detailed analysis of the Pim-1 gene demonstrated that the alterations observed in most MNU-induced and spontaneous tumours resulted from proviral integration at the 3' end of this gene. Our analyses also demonstrated that the majority of MNU-induced tumours, including those containing rearrangements in the Pim-1 gene, lacked the somatically acquired recombinant MCF proviruses that are present in most spontaneous AKR lymphomas. These results provide evidence that the mechanisms of development of MNU-induced and spontaneous tumours in AKR mice are distinct and the development of thymomas that contain proviral integrations at the Pim-1 locus in the MNU-treated AKR mice involve cooperation between the chemical carcinogen and endogenous murine leukaemia viruses.

Thymoma associated with rheumatoid arthritis in a patient taking methotrexate.

Recently many patients with rheumatoid arthritis (RA) have been effectively treated with methotrexate. Until now, there have been no treatment related neoplasms reported in patients with RA taking methotrexate. Furthermore, there have been no reports of thymoma associated with isolated RA. We describe a patient with classical RA who developed a thymoma while being treated with methotrexate.

Comparison of chemically induced and spontaneous murine thymic lymphomas in RF and AKR mice: differential expression of c-myc and c-myb.

Expression of 11 cellular oncogenes was determined in normal vs. lymphomatous thymic tissues of RF and AKR mice; only c-myc and c-myb transcripts were detected in an age-inappropriate pattern in thymomas. Normal thymocytes from young RF mice contained RNA transcripts of both genes, but the transcripts were no longer detected at 9 or more weeks of age. More than 90% of RF thymomas, occurring at 20-28 weeks of age after skin painting with 3-methylcholanthrene at 12 weeks, contained c-myc transcripts, and 70% of the tumors contained c-myb transcripts. Seven cell lines derived from these 3-methylcholanthrene thymomas expressed both cellular genes, as did 2 rare spontaneous thymomas of 12-month-old RF mice. No indication of rearrangement or amplification of either gene was seen in any of the RF tumors or cell lines. In AKR mice, transcripts of the 2 genes persisted longer in the normal thymus than in RF mice, but they were no longer detected at 26 weeks of age. Of 3 thymomas in 6-month-old 3-methylcholanthrene-treated AKR mice, all expressed c-myb and 2 expressed c-myc. Among 11 spontaneous AKR thymomas, however, only 2 showed detectable levels of both genes, and 2 more expressed c-myc or c-myb but not both.

Pathology of chronic polychlorinated biphenyl (PCB) feeding in rats.

The hepatocarcinogenic effect of Clophen A 30 and Clophen A 60 was tested in male weanling rats by long-term feeding over a period of 832 days. The mortality rate was investigated in 100-day intervals. In the first 800 days liver carcinoma accounted for 21% of necropsies in the Clophen A 60 group but only 2% of the necropsies in the Clophen A 30 group and none in the control animals. The tumors were first observed after 700 days. After 800 days hepatocellular carcinoma was the most common lesion observed in the Clophen A 60 animals (61%) whereas it was only observed in 3% of animals in the Clophen A 30 group and 2% in the controls. Preneoplastic lesions, such as foci of hepatocellular alterations and neoplastic nodules, were first observed after Day 500. The incidence of foci predominated in all time intervals, but an increase in neoplastic nodules and hepatocellular carcinomas was observed with increased time. There was a marked trend from foci to neoplastic nodule to hepatocellular carcinoma with time. The total mortality rate and the incidence of thymoma, inflammatory lesions of the urogenital tract, in the experiment were significantly reduced by Clophen administration. Whether this protective effect could be induced by polychlorinated biphenyls (PCBs) is discussed.

Autoimmune haemolytic disease in mice after exposure to a methylating carcinogen.

N-Methyl-N-nitrosourea (MNU) but not methyl methanesulphonate (MMS) induced both autoimmune haemolytic anaemia and thymic lymphoma in susceptible strains of mice, particularly the C57BL/6. These effects could be positively correlated with the formation of O6-methylguanine in target DNA. All murine lymphoid cells showed lack of ability to remove O6-methylguanine from their DNA, therefore the variation of responses between different mouse strains indicated that other host factors, probably genetic, must be involved. The results do indicate however that a potent pre-mutagenic DNA base modification can initiate the events leading to autoimmune disease in susceptible mice.

Carcinogenesis by derivatives of 1-nitroso-3,5-dimethylpiperazine in rats.

Four mononitrosopiperazines were administered to groups of 20 female Fischer 344 rats to compare their effectiveness as carcinogens. The four, 1-nitroso-3,5-dimethylpiperazine, its 4-acetyl derivative, its 4-benzoyl derivative, and 1-nitroso-3,4,5-trimethylpiperazine, were given as 0.7 mM solutions in drinking water, 100 ml to each rat per week. The length of treatment varied from 26 weeks for nitrosotrimethylpiperazine to 50 weeks for 1-nitroso-3,5-dimethyl-4-benzoylpiperazine. Dimethyl- and trimethylnitrosopiperazine gave rise to virtually 100% incidence of undifferentiated lymphomas of the thymus and leukemias within 30 weeks (in contrast to the non-C-methylated analogs which are noncarcinogenic or only weakly so). Acetyldimethylnitrosopiperazine was also a potent carcinogen, all of the rats treated with it dying within 30 weeks with tumors of the esophagus. In contrast, benzoyldimethylnitrosopiperazine was weakly carcinogenic, inducing only a small number of tumors of the forestomach and reducing the normal life span of the rats very little.

Carcinogenesis and aging. I. Modifying effects of aging on N-methyl-N-nitrosourea-induced carcinogenesis in female rats.

3- or 14-month-old female rats were intravenously injected N-nitroso-N-methylurea (MNU), 50 mg/kg body weight, 2 or 4 times weekly. There was a direct correlation between the incidence of mammary carcinomas and MNU doses. Kidney tumors occurred inversely proportional to the dose of the carcinogen. Mammary adenocarcinomas were only observed in young MNU-treated rats. Cervicovaginal malignant tumors were only observed in old MNU-treated rats. The incidence of hematopoietic system tumors was the same in animals of both age groups. Rats treated with MNU showed acceleration of benign spontaneous tumor development. The effect of aging on the initial stage of MNU-induced carcinogenesis is believed to be determined by age-associated changes in the proliferative activity of target tissues. The effect of aging on the further development of carcinogenesis may be caused by age-associated hormonal, metabolic, and immunological shifts.

Methylnitrosourea induction of thymomas in AKR mice requires one or two "hits" only.

Induction of thymomas by methylnitrosourea in many strains of mice requires 3 "hits". AKR mice develop thymomas spontaneously late in life, probably because of their large load of viral leukemia oncogenes. It was expected therefore, and so found, that methylnitrosourea induces thymomas in AKR mice with only 1 or 2 "hits". The viral oncogene therefore appears to function as a dominant "hit" gene cooperating with the chemical carcinogen.